JPH0623903B2 - Fixing device - Google Patents

Description

The present invention relates to a fixing device provided in a recording device such as an electrophotographic device or an electrostatic recording device, and more specifically, to an object to be fixed such as an unfixed image is subjected to a heat treatment and a pressure treatment. Alternatively, the present invention relates to a fixing device in which an offset generated during heat and pressure treatment is extremely well prevented.

In order to prevent the winding (jam) of conventional copy paper,
JP-B-57-41793 and JP-A-56-143474.
It is known to bring a fixing roller into contact with an antistatic brush as disclosed in Japanese Patent Laid-Open Publication No. 2000-242242, and to apply an AC bias to the fixing roller via the antistatic brush.

However, in any case, if the static elimination brush is contaminated with toner or paper dust, the static elimination efficiency will be drastically reduced. That is, the deterioration with time was large and the durability was poor.
Further, in order to prevent toner offset to the fixing roller, JP-A-55-55374 and JP-A-55-9697.
As disclosed in No. 0, a bias voltage having the same polarity as the toner is applied to the roller on the side that comes into contact with the toner image surface of the copy paper. Alternatively, it is known to apply a bias voltage having a polarity opposite to that of the toner to the roller on the side opposite to the toner image surface of the copy paper. However, when applied with a corona charger such as a corotron, not only does the device become large and complex and the cost increases, but when the corona charger becomes dirty, spark discharge and leaks easily occur, resulting in poor reliability, safety, and durability. It was scarce. Moreover, when applied by a bias roll, the effect was small.

An object of the present invention is to improve the above-mentioned conventional drawbacks with a simple structure, to minimize toner offset, and to secure a stable fixing performance.

The present invention solves the problem of causing a leak or discharge by applying a predetermined bias in the prior art, enables a large number of voltages to be applied, and efficiently prevents offset.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a heat fixing device according to an embodiment of the present invention.
The heating roller 1, which is provided as a fixing roller having the heater 3 built therein, receives a driving force from a driving motor (not shown) and rotates in the arrow direction. Reference numeral 2 denotes a pressure roller having a built-in low heating heater 3a, which is brought into pressure contact with the heating roller 1 to rotate by sliding.

In this heating roller 1, a metal hollow roller core 1a made of aluminum, stainless steel, steel or the like is provided with a heat-resistant release resin coating layer 1b of 20 to 100 .mu. . The pressure roller 2 is rotatably supported by a bearing (not shown). The pressing roller 2 is pressed against the heating roller 1 by a known pressing means at least at the time of fixing, and the elastic layer 2b of silicon rubber, fluorine rubber, fluorosilicone rubber or the like is attached to the outer peripheral surface of the metal roller core 2a.
Is relatively thick. The purpose of this structure is to secure a pressure contact area d with the heating roller 1. A temperature sensitive element 4 such as a thermistor or a thermocouple is arranged in contact with the outer peripheral surface of the heating roller 1, and a detection signal of the temperature sensitive element 4 is guided to a known control means (not shown) to heat the temperature of the outer peripheral surface of the heating roller 1. The toner image melting temperature is maintained by controlling the output of the heater 3 or its applied voltage. 5a,
Reference numeral 5b is a separation claw for surely separating the fixed copy paper P from the rollers 1 and 2.

Reference numeral 6 denotes a cleaning member for removing foreign matter such as offset toner and paper dust adhered to the surface of the heating roller from the roller surface. The cleaning web 6 is made of heat resistant nonwoven fabric such as Nomex (registered trademark) or Himeron (registered trademark).
a is used.

The cleaning web 6a is brought into contact with the heating roller 1 by a pressing roller 6c having elasticity such as silicone rubber, fluorine rubber, fluorosilicone rubber, silicone rubber sponge. Further, the web 6a is moved by the take-up roller 6d to be driven so as to slightly change its contact position from the supply roller 6b, and the new surface of the cleaning web 6a is always in contact with the heating roller. A guide plate 7 guides the copy paper P carrying the toner image T to the heating roller 1 side. Reference numeral 8 denotes an offset prevention member, which is a conductive base member 8a in which a large number of conductive needle-shaped members 8b are embedded. A bias power source 9 applies a DC voltage to the conductive base member 8a. The conductive needle-shaped member 8b is made of a flexible conductive fiber such as metal fiber or carbon fiber.

In FIG. 1, the heating roller 1 has an outer diameter of 60 mm and a wall thickness of 7 m.
As a pressure roller 2 and a roller in which a 30 μm thick PFA heat-resistant release resin coating layer 1b is provided on an aluminum core metal 1a having a thickness of 5 mm, a heat-vulcanizing silicone rubber having a thickness of 5 mm is formed on a stainless steel roller core 2a. A3 pattern paper 23 is pressed under a total pressure of 60 kg using a roller having an outer diameter of 60 mm provided with the elastic layer 2b.
Copying was performed at a speed of sheet / minute (roller peripheral speed 270 mm / sec).

The voltage of the bias power supply 9 is set to V ₁ =
_{-2KV, V 2 = -1KV, V} 3 = -0.5KV, V 4
= 0, V ₅ = 1KV, V ₆ (without offset prevention device)
When changed and tested, the corresponding heating roller 1
Of the surface of the heat-resistant mold-releasing resin coating layer 1b is V ₁ = −30
_{0V, V 2 = -120V, V} 3 = + 10V, V 4 = + 6
0 V, V ₅ = + 400 V, V ₆ = + 100 V, and the corresponding heat-resistant release resin coating layer 1 b of the heating roller 1 corresponding thereto.
The offset toner amount on the surface of the toner is expressed as a weight ratio (%) to the total toner amount on the copy paper P, T ₁ = 0.15, T
_{2 = 0.20, T 3 = 0.40} , T 4 = 0.40, T 5
= _0.90, and T 6 = 0.60.

From the above numerical values, it can be seen that the amount of offset toner decreases when a negative bias voltage is applied to the conductive needle member 8 using a negative polarity toner. Conversely, when a positive voltage is applied, the amount of offset toner increases. For example, when a bias voltage of -2 KV is applied, the amount of offset toner is reduced to 1/4 that in the case where there is no offset prevention device.

That is, when a DC bias voltage having the same polarity as the toner is applied to the side of the copy paper P on which the toner image T is facing, the offset is extremely reduced. Even after applying a bias voltage of -2 KV and attaching a toner image of about 300 mg / A3 · 1 sheet onto a copy sheet to make a copy of 100,000 sheets, the offset toner amount remains almost unchanged, and a good result is obtained. Was obtained.

FIG. 2 is a vertical sectional view showing a heating device according to another embodiment of the present invention. Reference numeral 10 denotes an outer diameter φ30 having a room temperature vulcanizing type silicone rubber coating layer 10b having a thickness of 6 mm on an aluminum core metal 10a.
Is a fixing roller. 11 has a 500 W halogen heater 12 built-in, and has a 30 μm thick PF on an aluminum core metal 11a.
The pressure roller 11 has an outer diameter of φ30 and is covered with the A coating layer 11b, and rotates in pressure contact with the fixing roller 10 at a total pressure of 30 kg.
Reference numeral 13 is a heating roller having an outer diameter of 15φ, in which a halogen heater 12a of 300 W is installed, and an aluminum core metal 13a is provided with a hard chrome plating 13b. Reference numeral 8 is an offset prevention member in which a conductive needle member 8b is implanted in a conductive substrate 8a, and 9
Is a bias power source, and the aluminum core metal 1 of the pressure roller 11
1a is electrically floated. This float means not electrically grounded or substantially electrically insulated, preferably electrically isolated.

As the toner T, a negatively charged toner was used, and when a bias of +2 KV was applied to the conductive needle-shaped member 8b by the bias power source 9, the offset toner was reduced to about 1/3.

That is, the pressure roller 11 on the side opposite to the toner image T of the copy paper P
When the bias of the positive polarity opposite to the negative polarity of the toner T is applied to the toner T, the offset toner is extremely reduced.

Also, in the above state, about 300 mg / A on copy paper
50,000 sheets (13 sheets /
After the copying, the amount of offset toner was almost unchanged and good results were obtained. When observing the conductive needle-shaped member 8b after passing 50,000 sheets, toner, paper powder, dust, etc. were found to be attached to the side surface 8d, which is the tip 8c, and was contaminated, but the tip 8c was very clean. It was.

3A is a side view showing still another embodiment, and FIG. 3B is a perspective view showing a case where the present invention is applied to a pressure fixing device. 14 is 60μ on the steel core 14a
It is a fixing roller having an outer diameter of 40φ provided with a thick PFA coating layer 14b and is electrically floated. Reference numeral 15 designates a fixing roller having an outer diameter of 40φ, which is formed by hard chrome plating on a steel material.
Reference numeral 5 is a pressure roller having an outer diameter of 40φ formed by hard chrome plating on a steel material, both of which are spacers 16a, 16 made of polyimide film provided at both ends of the fixing roller 14.
They are arranged opposite to each other by a gear tape 17 of 30 μm by b. The toner used is negatively charged toner for pressure fixing containing polyethylene as a main component, and −2 KV is applied from the bias power source 9 to the offset prevention member 8 to copy the unfixed toner image T on the copy roller 14 side. Once fixed, very good results were obtained.

In the present embodiment, by coating the surface of the fixing roller 14 with PFA, the amount of offset toner can be reduced to 1/5 or less as compared with a roller in which a steel roller is provided with hard chrome plating, and the PFA coating is performed. By applying a bias voltage of -2 KV to the surface by the offset prevention member 8 made of the conductive needle-shaped member 8b, the amount of offset toner can be further reduced to 1/3.

Next, as a comparative example, the cores 1a, 11a and 14a of the heating roller 1, the pressure roller 11 and the fixing roller 14 coated with the PFA thin film shown in FIGS. 1, 2 and 3 are electrically floated. If the bias voltage is applied by the conductive needle member 8b without grounding, the absolute value of the applied voltage will be 300
When the voltage exceeds V, a leak occurs between the PFA coating on the surface and the core metal, and it is impossible to apply a sufficient voltage to each roller surface to reduce the toner offset.

In addition, the tip of the conductive needle member 8b is connected to the rollers 1, 11,
In the case of contacting with No. 14, about 30,000 sheets in the first embodiment, the second
The toner offset to the rollers 1, 11 and 14 increased sharply after about 10,000 sheets in the embodiment and about 5000 sheets in the third embodiment. For example, when the tip portion 8c of the conductive needle member 8b shown in FIG. 2 is brought into contact with the surface 11b, paper powder, toner,
This is because the surface of the pressure roller 11 cannot be provided with an effective charge by being contaminated with silicone oil, and if the 8d surface (side surface) of the conductive needle-shaped member 8b is brought into contact with the surface PFA coating layer 11b, the contaminated portion will become dirty. That is, the tip portion 8c is kept in a clean state and the electric charge due to the bias can be supplied to the coating layer 11b on the roller surface for a long time.

In the third embodiment, the PFA coating is used as the thin insulating coating for charging the roller, but the PTFE coating is used outside.
(Polytetrafluoroethylene), heat-vulcanizable silicone rubber, room temperature vulcanizable silicone rubber, low temperature vulcanizable silicone rubber, Fluoro rubber, fluorosilicone rubber, polyimide,
Polyamide or the like can be applied.

Furthermore, the method of applying a bias with a conductive needle member does not require a high voltage unlike a corona charger, and can be processed at a low voltage.

Further, although the negatively charged toner is used in the embodiment, the polarity of the bias may be reversed when the positively charged toner is used.

As described above together with the effects of increasing the numerical values, at least one of the pair of fixing rollers has a thin insulating coating on a metal cored bar, and the cored bar of the roller is electrically floated, It is said that the tip of the flexible conductive needle-shaped member and the side surface following the tip are brought into contact with each other over the longitudinal direction of the roller, and a low voltage DC is applied to the roller surface from the low-voltage source via the conductive needle-shaped member. With a simple structure, it was possible to provide a fixing device for an electrophotographic apparatus, which can minimize the amount of offset toner by utilizing the action of electrostatic force and can perform stable copying for a long period of time.

As described above, according to the present invention, the conductive core material such as the roller core metal is electrically floated and the bias voltage is applied to the roller surface through the conductive member. Since leakage from the member to the conductive core material can be prevented and a desired voltage can be applied to the insulating layer, the offset can be stably and efficiently prevented efficiently.

In the embodiment of the present invention, since the tip of the conductive member and the side surface following the tip are brought into contact with the roller surface, the effect can be maintained for a long time.

In addition, the present invention has a conventional predetermined voltage of, for example, 20 KV / mi.
It is possible to solve the problem that the roller of a thin insulating layer that is grounded when a voltage of 8,000 V or less is applied is leaked by discharge and cannot be brought into a predetermined state. Such a conventional problem often occurs in a roller having an insulating layer of 500 μm or less or a thin insulating layer in which the above-mentioned leak discharge has occurred, but the present invention can solve these problems.

The present invention is particularly effective for such a roller having a thin insulating layer, and particularly excellent for a roller having a thickness of 200 μ or less.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention, FIG. 2 is a vertical sectional view showing another embodiment of the present invention, and FIG. 3 (a) is a side view showing still another embodiment of the present invention. FIG. 3 (b) is a perspective view of FIG. 3 (a). 1 ... Heating roller, 1b ... Heat-resistant release resin coating layer, 8
...... Offset prevention member, 8b ...... Conductive needle member, 9
...... Bias power supply, 11 ...... Pressure roller, 14 ...... Fixing roller, 11b, 14b ...... PFA coating layer.

 ─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP-A-55-55374 (JP, A) JP-A-56-143474 (JP, A) JP-A-55-96970 (JP, A) JP-A-59- 109077 (JP, A) Actually opened 55-84650 (JP, U) Actually opened 58-23356 (JP, U) Actually opened 57-164770 (JP, U) Actually opened 57-60161 (JP, U) Actual Public Sho 61-4920 (JP, Y2) Actual Public Sho 58-19564 (JP, Y2)

Claims (1)

[Claims] 1. A conductive core material for sandwiching and transporting a recording material for fixing an image composed of toner charged to a predetermined polarity, and an insulating surface having a layer thickness of 500 μm or less provided on the conductive core material. In a fixing device having a fixing roller having a layer, a conductive member in contact with the surface of the fixing roller, and a bias power source for applying a bias voltage to the conductive member, the conductive core material is in an electrically floating state. The fixing device according to claim 1.